The present invention relates to a method of respinning-in on open-end spinning machines after removing a fully wound bobbin from the swinging arms of a bobbin holder or prior to spinning at an empty spinning station, and to a device for carrying out the method.
Open-end spinning machines have undergone rapid development. They are automated to a considerable extent and are generally known to have attending devices which permit operation without human intervention. Up till now, three basic methods have been used during bobbin exchange with subsequent spinning-in, with some slight differences existing between each method.
A first method permits the bobbin exchange without interrupting the spinning process and consequently without any need for respinning. A new tube is inserted into the spinning machine while the operating station is running. During the bobbin exchange operation, the yarn is usually taken up or sucked off into a collector. When the bobbin exchange operation is finished, the sucked-off yarn is separated and applied to the new bobbin. This method has at least three drawbacks. First, there is a loss of the deviated yarn. Second, the method is not suitable for high delivery speeds because the mechanism carrying out the bobbin exchange is forced to work at high speeds undergoing considerable dynamic forces, with a resulting adverse effect on its service life. Third, this method is inapplicable to a standing operation unit, i.e., the beginning of a spinning cycle.
This third drawback, i.e., the problem arising at the beginning of a new spinning cycle, has been eliminated by a method in which at each bobbin exchange the spinning process is interrupted for a necessary time interval, so that the spinning unit can be cleaned prior to the respinning of the yarn. The yarn required for the respinning-in is obtained from wound yarn carried by a respective automative device. The bobbin exchange is the insertion of any empty tube into the machine arms which is carried out during the spinning operation similar to the first method. Therefore, this method has the same drawbacks of the first method.
For this reason, another method exists in which the spinning process of the operation unit in question is stopped or interrupted while the fully wound bobbin is being replaced by an empty tube. To permit the subsequent spinning-in and the automatic spinning resumption, a special mechanism provides a basic winding to the tube wherein the yarn is of a length sufficient enough for at least one spinning-in prior to the tube being fixed in the winding arms. This method permits the automative device to operate at very high delivery speeds since the bobbin exchange takes place with the operation station at rest and is therefore independent of the delivery speed.
Tests have shown that on a tube fitted with only a few initial windings of yarn, in particular on a perforated tube but to a lesser degree on a conical tube as well, the search for the yarn end carried out by the suction tube of the attending automatic device often causes disorder and irregular interlacing with other neighboring yarn windings, thus disturbing the spinning-in process and reducing the reliability of the bobbin exchange. Also, the spinning-in process has proved that it is impossible to create a spinning-in sector of yarn that is unnoticeable. There is always a detectable fault in the yarn appearance. Besides, the yarn used for the initial starting windings on the tube is not identical with the yarn just being produced at the operation unit or station in question. At first sight, these objections may appear trifling, but it is a fact that in goods such as knitwear, slight deviations in the yarn are visible faults. Moreover, the steadily increasing delivery speeds of the open-end spinning machines increase the desirability of carrying out the bobbin exchange with the operation unit at rest in order to avoid excessive requirements on the attending mechanisms, and to ensure at the same time that neither the initial (starting) windings nor the spun-in yarn sector are included into the finished products in the subsequent operations.